Coated particles and sunscreen and cosmetic products containing same

Abstract

Particles have an ultrathin, conformal coating are made using atomic layer deposition methods. The base particles include ceramic and metallic materials. The coatings can also be ceramic or metal materials that can be deposited in a binary reaction sequence. The coated particles are useful as fillers for electronic packaging applications, for making ceramic or cermet parts, as supported catalysts, as well as other applications.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims benefit of U.S. Provisional Application No. 60 / 810,362, filed Jun. 2, 2006, and of U.S. Provisional Application No. 60 / 843,445, filed Sep. 8, 2006.BACKGROUND OF THE INVENTION [0002] This invention relates to particulate materials that are useful as sunscreen agents, and to topical sunscreen or cosmetic compositions containing sunscreen agents. [0003] Topical sunscreen products protect the skin from the effects of harmful ultraviolet (UV) radiation by preventing the transmission of that radiation through absorption and scattering processes. A variety of sunscreen agents have been used in such products. One type of sunscreen agent that is widely used is a particulate metal oxide. Titanium dioxide and zinc oxide particles are most commonly used. Sometimes combinations of these are used. [0004] The difficulty with using metal oxides as the active sunscreen agent is that it is difficult to formulate a product that is t...

AI Technical Summary

Benefits of technology

In reaction A1, reagent M1Xn reacts with one or more M*-Z-H groups on the surface of the particle to create a new surface group having the form -M1-X. M1 is bonded to the particle through one or more Z atoms. The -M1-X group represents a site that can react with water in reaction B1 to regenerate one or more hydroxyl groups. The water can in some cases be replace with other oxidizing agents such as hydrogen peroxide (H2O2) or ozone (O3). In some cases, the M1Xn compound is thermally degradable to the desired layer material and in such cases the second reagent can be omitted. The hydroxyl groups formed in reaction B1 can serve as functional groups through which reactions A1 and B1 can be repeated, each time adding a new layer of M1 atoms. Hydroxyl groups can be eliminated as water, forming M1-O-M1 bonds within or between layers. This condensation reaction can be promoted if desired by, for example, annealing at elevated temperatures and / or reduced pressures. The subscript ‘n’ in reaction A1 is not necessarily a whole number, as processing conditions, as well as post treatments, may be used to preferentially alter the stoichiometric ratio to enhance the effectiveness of the invention.

[0029] Suitable M1X compounds for applying a zinc oxide film are diethyl zinc and dimethyl zinc. Suitable M1X compound for applying a titanium dioxide film are titanium tetraisopropoxide and titanium tetraethoxide. Suitable M1X compounds for applying a cerium oxide film are cerium tetramethylheptanedionate and cerium trimethylheptanedionate phenanthroline. In some cases, the corresponding metal halides can be used.

[0030] A reaction scheme for the deposition of TiO2 is described in Tsapatsis et al. (1991) Ind. Eng. Chem. Res. 30:2152-2159 and Lin et al., (1992), AlChE Journal 38:445-454, both incorporated herein by reference.

[0031] In addition, catalyzed binary reaction techniques such as described in copending application Ser. No. 08 / 942,522 entitled “Method of Growing Films on Substrates at Room Temperatures Using Catalyzed Binary Reaction Sequence Chemistry”, incorporated by reference, are suitable for depositing inorganic materials, especially oxide, nitride or sulfide coatings, most preferably oxide coatings. Reactions of this type can be represented as follows: M-F1+C1→M-F1—C1   (A4a) M-F1—C1+F2-M1-F2→M-M1-F2+F1—F2+C1   (A4b) M-M1-F2+C2→M-M1-F1—C2   (B4a) M-M1-F1—C2+F1-M-F1→M-M1-M-F1+F1—F2+C2   (B4b) C1 and C2 represent catalysts for the A4b and B4b reactions, and may be the same or different. F1 and F2 represent functional groups, and M and M1 are as defined before, and can be the same or different. Reactions A4a and A4b together constitute the first part of a binary reaction sequence, and reactions B4a and B4b together constitute the second half of the binary reaction sequence.

[0032] Except for the catalyzed reaction scheme described above, the binary reactions are generally performed at elevated temperatures, preferably from about 300-1000K. Between reactions, the particles are subjected to conditions sufficient to remove reaction products and unreacted reagents. This can be done, for example, by subjecting the particles to a high vacuum, such as about 10−5 Torr or less, after each reaction step. Another method of accomplishing this, which is more readily applicable for industrial application, is to sweep the particles with an inert purge gas between the reaction steps. This purge gas can also act as a fluidizing medium for the particles and as a carrier for the reagents.

[0033] Several techniques are useful for monitoring the progress of the reaction. For example, vibrational spectroscopic studies can be performed on high surface area silica powders using transmission Fourier transform infrared techniques. The deposited inorganic materials can be examined using in situ spectroscopic ellipsometry. Atomic force microscopy studies can be used to characterize the roughness of the coating relative to that of the surface of the substrate. X-ray photoelectron spectroscopy and x-ray diffraction can be used to do depth-profiling and ascertain the crystallographic structure of the coating. Mass Spectroscopy, or Residual Gas Analysis, downstream of the reactor can be utilized in situ to monitor gaseous products, then gaseous reactants, that pass through the reaction chamber while dosing each precursor. Once the reaction product is no longer generated, the reaction is complete and any additional precursor dosed into the system is wasted. A convenient method for applying the ultrathin deposits of inorganic material to the base particles is to form a fluidized bed of the particles, and then pass the various reactants in turn through the fluidized bed under appropriate process conditions. Methods of fluidizing particulate materials are well known, and generally include supporting the particles on a porous plate or screen. A fluidizing gas is passed upwardly through the plate or screen, lifting the particles somewhat and expanding the volume of the bed. With appropriate expansion, the particles behave much as a fluid. Fluid (gaseous or liquid) reagents can be introduced into the bed for reaction with the surface of the particles. In this invention, the fluidizing gas also can act as an inert purge gas for removing unreacted reagents and volatile or gaseous reaction products.

Problems solved by technology

The difficulty with using metal oxides as the active sunscreen agent is that it is difficult to formulate a product that is transparent and yet has a high sunscreen protection factor (SPF).

Similarly, many cosmetic products such as foundations are formulated to produce a specific color or tone, but cannot be done so when the metal oxide content is too high.

The organic sunscreen agents are often susceptible to photodegradation and / or chemical degradation by peroxides or other superoxides, hydroxyl compounds and / or free radicals.

Unfortunately, metal oxides often produce oxidants or free radicals of this sort when exposed to UV light.

As a result, the organic sunscreen agent can rapidly degrade when the product is exposed to sunlight, and the product SPF value drops rapidly.

Doping can dilute the efficiency of the metal oxide.

Several factors have made this difficult in practice.